Characterization of Anopheles gambiae Transglutaminase 3 (AgTG3) and Its Native Substrate Plugin
Journal of Biological Chemistry(2013)
Abstract
Male Anopheles mosquitoes coagulate their seminal fluids via cross-linking of a substrate, called Plugin, by the seminal transglutaminase AgTG3. Formation of the "mating plug" by cross-linking Plugin is necessary for efficient sperm storage by females. AgTG3 has a similar degree of sequence identity (similar to 30%) to both human Factor XIII (FXIII) and tissue transglutaminase 2 (hTG2). Here we report the solution structure and in vitro activity for the cross-linking reaction of AgTG3 and Plugin. AgTG3 is a dimer in solution and exhibits Ca2+-dependent nonproteolytic activation analogous to cytoplasmic FXIII. The C-terminal domain of Plugin is predominantly alpha-helical with extended tertiary structure and oligomerizes in solution. The specific activity of AgTG3 was measured as 4.25 x 10(-2) units mg(-1). AgTG3 is less active than hTG2 assayed using the general substrate TVQQEL but has 8-10 x higher relative activity when Plugin is the substrate. Mass spectrometric analysis of cross-linked Plugin detects specific peptides including a predicted consensus motif for cross-linking by AgTG3. These results support the development of AgTG3 inhibitors as specific and effective chemosterilants for A. gambiae.
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Key words
Analytical Ultracentrifugation,Circular Dichroism (CD),Protein Expression,Transglutaminases,X-ray Scattering
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